Imaging device and electronic device

Abstract

Provided are an imaging device and an electronic device capable of improving the charge transfer characteristic. The imaging device includes a semiconductor substrate and a vertical transistor provided on the semiconductor substrate. The semiconductor substrate is provided with a hole opened to the first main surface side. The vertical transistor includes a first gate electrode provided inside the hole, and a second gate electrode provided outside the hole and connected to the first gate electrode. The first gate electrode includes a first part and a second part including a material having conductivity different from conductivity of the first part.

What is claimed is: 
     
         1 . An imaging device comprising
 a semiconductor substrate, and   a vertical transistor provided on the semiconductor substrate, wherein:   the semiconductor substrate is provided with a hole opened to a first main surface side;   the vertical transistor includes   a first gate electrode provided inside the hole, and   a second gate electrode provided outside the hole and connected to the first gate electrode; and   the first gate electrode includes   a first part, and   a second part including a material having conductivity different from conductivity of the first part.   
     
     
         2 . The imaging device according to  claim 1 , wherein
 the first part is located between the second part and the second gate electrode.   
     
     
         3 . The imaging device according to  claim 1 , wherein
 the first part and the second part face each other in a direction parallel to the first main surface.   
     
     
         4 . The imaging device according to  claim 1 , wherein
 each of the first part and the second part includes a semiconductor of a first conductivity type, and   an impurity concentration of the first conductivity type in the second part is lower than an impurity concentration of the first conductivity type in the first part.   
     
     
         5 . The imaging device according to  claim 4 , wherein
 the first gate electrode further includes a third part that is located on an opposite side of the first part with the second part interposed therebetween and includes a semiconductor of a first conductivity type, and   an impurity concentration of the first conductivity type in the third part is lower than an impurity concentration of the first conductivity type in the second part.   
     
     
         6 . The imaging device according to  claim 1 , wherein
 the first part includes a semiconductor of a first conductivity type, and   the second part includes a non-doped semiconductor.   
     
     
         7 . The imaging device according to  claim 1 , wherein
 the first part includes a semiconductor of a first conductivity type, and   the second part includes a semiconductor of a second conductivity type.   
     
     
         8 . The imaging device according to  claim 1 , wherein
 the first part includes a semiconductor of a first conductivity type, and   the second part includes metal.   
     
     
         9 . The imaging device according to  claim 1  further comprising
 a photoelectric conversion unit provided on the semiconductor substrate, and 
 a charge holding unit that is provided on the semiconductor substrate and holds charge generated in the photoelectric conversion unit, wherein 
 the vertical transistor is used as a transfer transistor that transfers charge from the photoelectric conversion unit to the charge holding unit. 
 
     
     
         10 . An electronic device, comprising:
 an optical component;   an imaging device on which light transmitted through the optical component is incident; and   a signal processing circuit that processes a signal output from the imaging device, wherein:   the imaging device includes   a semiconductor substrate, and   a vertical transistor provided on the semiconductor substrate;   the semiconductor substrate is provided with a hole opened to a first main surface side;   the vertical transistor includes   a first gate electrode provided inside the hole, and   a second gate electrode provided outside the hole and connected to the first gate electrode; and   the first gate electrode includes   a first part, and   a second part including a material having conductivity different from conductivity of the first part.